Well the (limited, but still) testing I've done at work tells me 3Gbps interface is enough for a single SSD, and write speeds on better generation 2/3 SSDs at least are on par with mechanical drives.
Have only used them in Vista/Win7 but supposedly drive alignment needs to be adjusted manually for XP installs, and TRIM also works best with for example Win7 (less wear on the SSD supposedly).
Access times and burst read speed are good, that's for sure.